Two of the major functions of the seats found in vehicles are to provide for the comfort and the safety of the occupants. Modern vehicle seats are often adjustable. In particular, the forward most edge of the cushioned seat base on which the occupant sits is frequently configured to extend outwards relative to the backrest of the seat, for example to improve comfort for occupants with longer legs. While some adjustable seats of this kind comprise a secondary cushion cassette which moves to extend the seat edge while the main seat base cushion remains stationary, other versions involve the forward movement of the entire cushion of the seat base along with the underlying seat structure.
Vehicle seats are also commonly fitted with occupant classification systems (OCS). These systems detect the presence of a passenger, and can determine their approximate weight and seating position. A primary function of these systems is to control the deployment of airbag systems. As rapid airbag deployment can be dangerous to occupants, particularly children, infants and smaller adults; and those positioned closer to the airbag, the weight and position data collected by the OCS can be used to reduce the speed of airbag deployment or disable it entirely. In the United States, advanced airbag systems which use this kind of technology are mandated by law.
A typical OCS installed in the seat base comprises a “bladder” filled with a flowable material, such as a liquid or gel, and connected by a hose to a transducer. The transducer is typically a pressure sensor. The bladder may be in the form of a tubing arrangement or a mat, or a combination thereof. The pressure sensor communicates with an electronic control unit, so that when someone sits on the seat where the OCS is installed, the material in the bladder is displaced and is registered by the pressure sensor which in turn sends a signal to the control unit that the seat is occupied. By means of one or more sensors, it is possible also to ascertain the occupant's weight and/or position on the seat which information may also be conveyed to the control unit. The control unit then transmits data to the associated airbag which will also have its own electronic control unit.
The components comprising the OCS are commonly supplied by a third party, making it frequently impractical to adapt these components to the particular configuration of the seat to which they are fitted. For safety and operational reasons, strict guidelines regulate the relationships both between the components of the OCS, and between those components and the components of the seat. For instance, it is vital that the hose between the bladder and the pressure sensor is not constricted. Suppliers of OCS may stipulate that the hose is routed such that it does not interfere, foul or become entangled with any other seat component during movement of the seat when the seat is occupied.
It is therefore an object of at least certain embodiments of the invention to provide an adjustable vehicle seat suitable for use with an OCS which allows for the forward movement of the seat base cushion without compromising the operability of the OCS.